Bitcoin is sliding

Bitcoin is flirting with a break below $2,500 a coin. The cryptocurrency trades down 3.7% at $2,510 and is threatening its lowest close since June 27. It's rival, ethereum is also under pressure, down 8% at $244.

Friday's slide comes amid a relatively quiet week for bitcoin. It's price has been locked in a range between $2,474 and $2,639 since Monday. That's the day when Sheba Jafari, the head of technical strategy at Goldman Sachs, warned in a note to clients that bitcoin could fall as low as $1,857 before surging as high as $3,915.

Recently, there has been a bit of skepticism surrounding the cryptocurrency. Back in early June, tech billionaire Mark Cuban said bitcoin was a "bubble." He tweeted, "I think it's in a bubble. I just don't know when or how much it corrects. When everyone is bragging about how easy they are making $=bubble."